Conventionally, packages containing drinks such as milk, juice, tea, and the like are formed from packaging paper materials laminated with plastic film, in view of reduced weight and prices of packages. In a package manufacturing apparatus for manufacturing such packages, a packaging paper material is fed longitudinally and undergoes longitudinal sealing so as to be formed into a tube, and the thus-formed tube is filled with contents. Subsequently, the tube undergoes lateral sealing and cutting, whereby a package in process of forming, i.e. a semi-finished package, is formed.
Then, when the semi-finished package is to be formed into a finished package, i.e. a final package, a portion-to-be-processed of the semi-finished package, for example, a sealed portion is folded onto the end face of the semi-finished package. Subsequently, a pair of flaps are formed at the folded sealed portion and folded onto the end face. Then, the shape of the tube is formed into a polygonal prism such as a hexagonal or octagonal prism.
In this case, the sealed portion of a semi-finished package must be favorably folded. To attain this end, a folding line is formed in the sealed portion of a semi-finished package through use of a dedicated folding-line-forming apparatus, and subsequently the sealed portion is folded along the folding line through use of a folding machine disposed separately from the folding-line-forming apparatus.
However, in the above conventional package manufacturing apparatus, the folding-line-forming apparatus is used to form a folding line, and the folding machine is used to fold the sealed portion. As a result, an actual fold may not be aligned with the formed folding line; i.e., the sealed portion may not be accurately folded along the formed folding line.
To solve the problem, the sealed portion can conceivably be folded while the folding line is being formed in the sealed portion. However, when a thick packaging material, a highly rigid packaging material, or a like packaging material is used, folding induces a large reaction force. This reaction force is apt to cause the misalignment between the folding line and an actual fold. As a result, not only does the sealed portion fail to be accurately folded, but also the sealed portion fails to be sufficiently folded, resulting in impaired appearance of a package.
An object of the present invention is to solve the problems involved in the conventional package manufacturing apparatus and to provide a package manufacturing apparatus capable of folding a portion-to-be-processed accurately along a folding line without misalignment between the folding line and an actual fold, to thereby improve the appearance of a package.